A very high performance stabilization system for large mass bolometerexperiments

Abstract CUORE is a large mass bolometric experiment, composed of 988 crystals, under construction in Hall A of the Gran Sasso Underground Laboratories (LNGS). Its main aim is the study of neutrinoless double beta decay of 130Te. Each bolometer is a 760 g crystal of Tellurium dioxide on which a Nuclear Transmutation Doped Ge thermistor, Ge NTD, is glued with proper thermal contact. The stability of the system is mandatory over many years of data taking. To accomplish this requirement a heating resistor is glued on each detector across which a voltage pulse can be injected at will, to develop a known calibrated heating power. We present the design solution for a pulse generator system to be used for the injection of such a small and short voltage pulse across the heaters. This system is composed by different custom PCB boards each of them having multi-channel independent outputs completely remotely programmable from the acquisition system, in pulse width and amplitude, through an on-board ARM7 microcontroller. Pulse amplitudes must be selectable, in order to handle each detector on its full dynamic range. The resolution of the output voltage is 12 bits over 10 V range. An additional 4 steps programmable voltage attenuator is added at every output. The width of any pulse can range from 100 μ s to 25.5 ms. The main features of the final system are: stability and precision in pulses generation (at the level of less than a ppm/°C), low cost (thanks to the use of commercial components) and compact implementation

Archeologia e fascismo negli archivi di Luigi Maria Ugolini

The rediscovery of the archives related to the research carried out in Malta by L. M. Ugolini on behalf of the Regime, together with the study of related documentation, allows us to reconstruct how Prehistory came to be used in the Twenties to justify Italian territorial aspirations in the Mediterranean. These theories contradicted Nordist claims that it was the Aryans who brought ci- vilization to the Mediterranean; they also put to rest the outdated view that the Phoenicians were responsible for the megalithic temples of Malta. In the course of his life, Ugolini acted as a voice of propaganda for the Regime. However, as staunch believer of Mediterraneanism, he worked tirelessly to highlight the grandeur of prehistoric cultures throu- ghout the Mediterranean, and sought archaeological evidence to support the anthropological theories of G. Sergi on the origins of the Mediterranean race.peer-reviewe

Characterization of high impedance connecting links for Bolometric detectors

Abstract High impedance connecting links and cables are tested at low frequency in terms of their parasitic impedance to ground and to neighboring connecting links. These parameters must be well characterized with detectors operated at low temperature, especially when the very front-end is at room temperature, which results in a long link. This is the case of the LUCIFER experiment, an array of crystals where every event of interest produces two signals, one composed of phonons, the other of photons. The parasitic impedance is usually considered to be the parallel combination of a resistance and a capacitance. We characterized both and found that from the static measurements the capacitance of the cable resulted much larger. On the basis of this result we optimized the measurement set-up and developed a model to account for this behavior

An ultra fast, low power readout chain for single photon sensitivity with multi-anode photomultiplier tubes for the RICH upgrade at LHCb

Abstract An upgrade proposal for the LHCb RICH detectors at the Large Hadron Collider at CERN is being developed at the INFN section of Milano Bicocca, based on multi-anode photomultiplier tubes. The application requires the fast readout of Cherenkov rings of photons, with single photon sensitivity, at an event rate up to 40 MHz. The proposed readout chain is tailored for the R7600 multi-anode photomultiplier tubes from Hamamatsu, which proved to fit the single photon sensitivity requirement. The readout electronics for each pixel will be composed of an analog pulse shaper, a binary discriminator and additional digital circuitry to count the pulses. A prototype of the analog shaper was built with commercial discrete transistors in Silicon–Germanium (SiGe) Heterojunction technology. The tradeoff between response speed and power dissipation was investigated; and power as low as a few mW per channel could be achieved with response times of the order of one nanosecond. Furthermore, noise and jitter were evaluated, showing very good performances of the prototype

Characterization of the Hamamatsu R11265-103-M64 multi-anode photomultiplier tube

The aim of this paper is to fully characterize the new multi-anode photomultiplier tube R11265-103-M64, produced by Hamamatsu. Its high effective active area (77%), its pixel size, the low dark signal rate and the capability to detect single photon signals make this tube suitable for an application in high energy physics, such as for RICH detectors. Four tubes and two different bias voltage dividers have been tested. The results of a standard characterization of the gain and the anode uniformity, the dark signal rate, the cross-talk and the device behaviour as a function of temperature have been studied. The behaviour of the tube is studied in a longitudinal magnetic field up to 100 Gauss. Shields made of a high permeability material are also investigated. The deterioration of the device performance due to long time operation at intense light exposure is studied. A quantitative analysis of the variation of the gain and the dark signals rate due to the aging is described.Comment: 22 page